1. Field of the Invention
This invention relates to a battery pack having a plurality of rectangular batteries connected in series and/or parallel, and in particular to a battery pack for use in a battery driven vehicle such as a hybrid electric vehicle (HEV) or a pure electric vehicle (PEV).
2. Description of the Related Art
Higher output in a limited space is sought for a battery pack or battery array used as a power source in an electric vehicle or hybrid car. Consequently, rectangular batteries have been used, which have energy density superior to that of circular cylindrical batteries. However, in this type of battery pack with a plurality of rectangular batteries connected in series and/or parallel, adjacent rectangular battery cells are in close disposition. Therefore, the ability to efficiently radiate heat is imperative. In particular, lithium ion batteries can for some reason experience thermal runaway, and separators are used to thermally insolate adjacent battery cells (for example, refer to Japanese Patent Application Disclosures 2006-48996 and 2004-362879). In addition, these types of separators, which are disposed between rectangular batteries using metal external, cases, also serve to electrically insolate those battery cells.